This invention relates to a device for attaching a sheet to a mattress.
A conventional bed comprises a generally rectangular mattress, which rests on a support structure. When the bed is made, a bottom sheet is placed on the mattress and is tucked in between the mattress and the support structure around all four edges of the mattress, a top sheet is placed over the bottom sheet and is tucked in at the foot of the bed and along most of two sides of the bed, and blankets or other bedcovers are placed over the top sheet.
The top sheet that is used with conventional mattresses is flat, i.e., it will lie flat, without folding, when spread out on a flat surface. However, it is conventional to employ a fitted sheet as the bottom sheet. A fitted sheet is not flat but is formed with pockets at the corners so that it will fit snugly about the mattress. The advantage of a fitted bottom sheet is that it normally stays securely in position. One difficulty with fitted sheets is that a fitted sheet for one size mattress cannot be fitted to a larger sized mattress, and the advantage of a fitted sheet is largely lost if it is fitted to a smaller sized mattress. Also, in recent years many mattress manufacturers have made mattresses that are thicker than those that they previously made, and sheepskin and so-called egg box mattress pads, which are thicker than the mattress pads that were previously used, have been introduced. Fitted sheets that have been made to fit a previously-conventional mattress, provided with a previously-conventional mattress pad, will not fit easily over a thick mattress that is provided with a thick pad.
U.S. Pat. No. 4,660,240 discloses a device for attaching sheets to a waterbed. A waterbed mattress contains water, and the support structure of a waterbed is normally in the form of a box-like frame in which the mattress is disposed. One attachment device is provided at each corner of the mattress. The attachment device comprises a short length of elastic tape, which is attached at one end to the frame, e.g. by means of a screw. At its other end, the elastic tape is attached to a two-part fastener. The two-part fastener is able to grip releasably one or two bed sheets. The two fasteners at the foot of the bed grip both the top and bottom sheets, while the fasteners at the head of the bed grip only the bottom sheet. The sheets are thus kept in position on the bed, without need for using fitted sheets.
U.S. patent application Ser. No. 07/034,424 filed April 3, 1987, now U.S. Pat. No. 4,782,543 show another attachment device for use with waterbeds. The device shown in that patent application comprises a generally flat retainer portion which is placed under the mattress, adjacent its corner. The weight of the mattress at its corner keeps the retainer portions in position. A strap extends from the retainer portion, and a two-piece fastener, similar to that shown in U.S. Pat. No. 4,660,240, is attached to the strap at its outer end. The strap is long enough that the retainer portion can remain under the mattress while the two-piece fastener is positioned close to the top of the mattress.
Neither of the sheet attachment devices referred to above is suitable for use with a bed having a spring or foam mattress With regard to U.S. Pat. No. 4,660,240, conventional beds having spring or foam mattresses do not have the type of frame that is used in a conventional waterbed, and it is not convenient to attach the elastic tape to the support structure of a conventional bed. With regard to the pending application, a spring or foam mattress often does not lie firmly on its support structure at its corners, and accordingly the retainer portion is not held in position sufficiently firmly.
It is known to attach a bed sheet to a spring or foam mattress by use of an attachment device comprising two garter clips secured to opposite ends of an elastically-extensible strap. A garter clip is not satisfactory for attachment of a bed sheet because stresses are concentrated over a very small area of the fabric of the sheet, and the tension in the sheet when the bed is in use often results in the garter clip tearing the fabric of the sheet. Moreover, because the strap is elastically extensible, the sheet is not held firmly in position. Furthermore, the attachment device cannot be used for attachment of both a top sheet and a bottom sheet, because the garter clip is only able to accommodate a single sheet.